The present invention relates to an electrical signal filter used in the cable industry, and in particular, an electrical signal filter housing including a drive member that facilitates easy installation of the filter to another device using a commonly available tool.
Various types of filters are used in the cable industry to manage signals transmitted via a cable line. For example, high pass filters are used to prevent the ingress of noise from individual subscriber""s televisions into the cable system, which noise would adversely affect the signal supplied to cable internet subscribers. As high pass filters require relatively simple circuitry, the housing that encloses the circuitry can be relatively small. In fact, some high pass filter manufacturers have made the housing in the shape of a hexagon having a span of {fraction (7/16)}xe2x80x3, to match the span of the hexagonal nut used on typical F-connectors used to terminate cable lines. As a result, the same {fraction (7/16)}xe2x80x3 wrench used to secure the F-connector to the filter can also be used to install the high pass filter to another device, such as a splitter.
Another type of filter used in the CATV industry is referred to as a notch or trap filter. This type of filter is used, for example, to add a scrambling signal to or remove a scrambling signal from a transmitted cable signal, to control a subscriber""s access to certain subscription channels. As the circuitry involved with such trap filters is much more complex compared to high pass filters, the filter housing tends to be substantially larger in diameter and length. The industry has adopted a circular filter housing having a diameter ranging from xc2xexe2x80x3 to 1xe2x80x3, to provide sufficient room to enclose the electronic components of trap filters.
One example of such a trap filter is shown in FIG. 1, which corresponds to FIG. 9 of U.S. Pat. No. 5,662,494, the entirety of which is incorporated herein by reference. FIG. 1. shows that the female connector end 1 of the filter housing includes two holes 2a, 2b, which are designed to receive a special tool that rotates the housing so that the male end 3 of the filter housing can be secured to another device, such as a directional tap or another filter in a cascading setup. While this technique is quite effective to provide a tight threaded connection between the male end 3 of the housing and the other device, it requires a special tool.
In addition, when a coaxial cable connector is secured to the female connector end 1 of the filter housing using a {fraction (7/16)}xe2x80x3 wrench, for example, the torque imposed on the housing by the wrench will also affect the torque at the male end of the housing. That is, if the torque imposed by the wrench exceeds that used to secure the housing to the other device, then the torque imposed by the wrench will be transmitted to the male end of the housing. This increased torque could be excessive with respect to the receiving hole of the device in which the male end of the housing is secured, which in turn could damage the other device.
In an effort to provide selective torque control at both ends of the filter housing, a channel lock wrench could be used to hold the outer surface of the filter housing while the cable connector is secured to the housing. However, in many filters, the outer housing can turn independent of the threaded female connector. Moreover, use of a channel lock wrench damages the outer surface of the filter, which can lead to corrosion, and, in extreme cases affects the electrical performance of the filter.
An alternative to using a channel lock wrench would be to form the outer filter housing in the shape of a hexagon having a span of 1xe2x80x3, for example. In this way, an installer could use an open end 1xe2x80x3 wrench to rotate the housing and secure it to another device at a predetermined torque. That same wrench could then be used to hold the filter housing and a {fraction (7/16)}xe2x80x3 wrench could be used to secure an F-connector-terminated cable on the threaded female connector portion of the filter housing. However, forming the filter housing in the shape of a hexagon is generally more expensive than using regular cylindrical tube stock, which is standard practice in the trap filter industry. Moreover, in cases where torque control is not a concern, such a filter housing would still require the use of two different tools to complete installation.
It would be desirable to provide a filter housing having a diameter exceeding {fraction (7/16)}xe2x80x3, that can be installed on another device using the same tool used to secure the cable connector to the filter, while also providing torque control at both ends of the filter housing.
It is an object of the present invention to overcome the above-discussed drawbacks with the prior art.
A first embodiment of the present invention provides an electrical signal filter housing of the type including a threaded female connector adapted to mate with a hexagonal cable connector having a span X, the filter housing comprising a body having a span Y, which is substantially greater than X, a threaded female connector portion having a base connected to a first end of the body, a male connector portion connected to a second, opposed end of the body, and a drive member disposed proximate the base of the threaded female connector portion, the drive member having a span substantially equal to X.
Preferably, the drive member includes at least two flat sides in substantial parallel relation to one another, and the span, X, between the two flat sides is equal to {fraction (7/16)}xe2x80x3. More preferably, the drive member is hexagonal and X is equal to {fraction (7/16)}xe2x80x3.
In accordance with a preferred method of the present invention, an electrical signal filter is installed between another device and a cable terminated with a cable connector having a span X, a housing of the electrical signal filter having a span Y which is substantially greater than X and a threaded female connector portion at one end thereof, the method comprising the steps of:
(a) providing a tool having an engaging span substantially equal to X;
(b) using the tool to engage a drive member, having a span X, positioned proximate the threaded female connector portion of the filter housing;
(c) rotating the filter housing to secure the filter to another device;
(d) using the same tool to engage the cable connector terminating the cable; and
(e) rotating the cable connector to secure the cable to the filter.
More preferably, the method further includes, between steps (c) and (d), the steps of:
(i) providing a second tool having an engaging span substantially equal to X;
(ii) using the second tool to engage the drive member; and
(iii) holding the second tool to prevent substantial rotation of the filter during step (e).
The electrical signal filter housing and installation method of the present invention allow the use of a conventional tool, such as a {fraction (7/16)}xe2x80x3 wrench, to secure the housing to another device, while also allowing for torque control at both ends of the housing. Accordingly, a {fraction (7/16)}xe2x80x3 wrench can be used to secure the housing to another device, and then the same {fraction (7/16)}xe2x80x3 wrench can be used to secure the cable connector to the threaded female connector portion of the housing. If it is desired to maintain the level of torque at the male end of the filter housing independent of the torque imposed on the female end of the housing, then another {fraction (7/16)}xe2x80x3 wrench can be used to hold the filter housing while the cable connector is being secured to the housing.
The present invention eliminates the need for a special tool to install the filter housing to another device, and also provides for selective torque control at both the male and female ends of the filter housing. This not only simplifies filter installation, but also provides a simple and efficient way to control installation torque at both ends of the filter housing that heretofore has not been available.